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substack-publisher-mcp

by dkships
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Remote

List Posts

list_posts
Read-onlyIdempotent

Retrieve published Substack posts with filters for type, date range, and sort order. Returns paginated post details including titles and URLs for analytics workflows.

Instructions

List posts published by a Substack publication. Returns { posts, next }: each post has post_id, title, subtitle, audience, postDate, urlSlug, and coverImage. next is a cursor for the following page, or null on the last page. Use urlSlug with get_post or get_post_stats.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
nextNoPagination cursor from a previous list_posts response. Pass this to get the next page of results.
typeNoFilter by post type.
sortByNoSort order. Defaults to newest.
endDateNoFilter posts published before this date (YYYY-MM-DD, exclusive). For a single day D, use startDate D and endDate D+1.
startDateNoFilter posts published on or after this date (YYYY-MM-DD).
maxResultsNoMaximum number of posts per page. Default 100. Prefer paginating with `next` over large values.
publicationNoPublication name (e.g., 'ny', 'la'). Required if multiple publications are configured.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed6 schema fields changedv1.2.0
    • changedInput schema / properties / endDate / description
      Previous value: -"Filter posts published on or before this date (YYYY-MM-DD)."New value: +"Filter posts published before this date (YYYY-MM-DD, exclusive). For a single day D, use startDate D and endDate D+1."
    • addedInput schema / properties / endDate / format
      Added value: +"date"
    • changedInput schema / properties / endDate / pattern
      Previous value: -"^\\d{4}-\\d{2}-\\d{2}$"New value: +"^(?:(?:\\d\\d[2468][048]|\\d\\d[13579][26]|\\d\\d0[48]|[02468][048]00|[13579][26]00)-02-29|\\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\\d|30)|(?:02)-(?:0[1-9]|1\\d|2[0-8])))$"
    • changedInput schema / properties / maxResults / description
      Previous value: -"Maximum number of posts to return. Default 100."New value: +"Maximum number of posts per page. Default 100. Prefer paginating with `next` over large values."
    • addedInput schema / properties / startDate / format
      Added value: +"date"
    • changedInput schema / properties / startDate / pattern
      Previous value: -"^\\d{4}-\\d{2}-\\d{2}$"New value: +"^(?:(?:\\d\\d[2468][048]|\\d\\d[13579][26]|\\d\\d0[48]|[02468][048]00|[13579][26]00)-02-29|\\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\\d|30)|(?:02)-(?:0[1-9]|1\\d|2[0-8])))$"
  2. Changed5 schema fields changedv1.1.0
    • removedInput schema / additionalProperties
      Removed value: -false
    • addedInput schema / properties / endDate / pattern
      Added value: +"^\\d{4}-\\d{2}-\\d{2}$"
    • addedInput schema / properties / maxResults / maximum
      Added value: +9007199254740991
    • addedInput schema / properties / maxResults / minimum
      Added value: +1
    • addedInput schema / properties / startDate / pattern
      Added value: +"^\\d{4}-\\d{2}-\\d{2}$"
  3. First observedv1.0.0

TDQS

A4.2/5.0
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already provide readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is covered. The description adds useful behavioral details: the response shape, the pagination cursor contract, and the fact that `next` is null on the last page.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is three sentences with no filler. It front-loads the operation, then provides the return shape and pagination semantics, all of which are essential for correct use.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Since there is no output schema, the description appropriately explains the return object and its fields. It leaves parameter details to the schema, which is acceptable given the high schema coverage. Minor details like sort defaults are handled by the schema descriptions.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so all parameters are already well documented. The description adds marginal reinforcement around `next` and urlSlug but does not need to explain filters or sorting because the schema covers them.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses a specific verb ('List') and resource ('posts published by a Substack publication') and describes the return shape, making the tool's purpose immediately clear. It also mentions using urlSlug with get_post or get_post_stats, which helps distinguish it from the single-post sibling tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description establishes clear context: this tool lists posts and supports pagination via the `next` cursor. It does not explicitly contrast with search_posts or state when not to use this tool, but the purpose is specific enough that an agent can infer when listing is appropriate.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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